Electrophotographic deposition of unpackaged semiconductor device

ABSTRACT

Described herein are techniques related a precision deposition of unpackaged semiconductor devices (“dies”) onto a substrate. This Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e)(1) of U.S.Provisional Application No. 62/009,094, filed Jun. 6, 2014, which ishereby incorporated by reference in its entirety.

BACKGROUND

Semiconductor devices are electrical components that utilizesemiconductor material (such as silicon, germanium, gallium arsenide,and the like). Semiconductor devices are typically manufactured assingle discrete devices or as integrated circuits (ICs). Examples ofsingle discrete devices include light-emitting diodes (LEDs), diodes,transistors, resistors, and the like.

The fabrication of semiconductor devices typically involves an intricatemanufacturing process with a myriad steps. The end-product of thefabrication is packaged semiconductor devices. A “packaged” modifierrefers to the enclosure and protective features built into the finalproduct as well as the interface that enables the device in the packageto be incorporated into an ultimate circuit.

The conventional fabrication process for semiconductor devices startswith a semiconductor wafer. The wafer is diced into a multitude ofunpackaged semiconductor devices. Herein, unpackaged semiconductordevices may be called semiconductor device dies. Indeed, the actionsbetween the wafer handling and the packaging can be called “diepreparation.” After such preparation, the conventional fabricationprocess packages each of the dies.

Typically, the packaging involves mounting a die into a plastic orceramic package (e.g., mold or enclosure). The packaging also includesconnecting the die pads to pins/wires for interfacing/interconnectingwith ultimate circuitry. The packaging of the semiconductor device istypically completed by sealing the die to protect it from theenvironment (e.g., dust, temperature, and/or moisture).

A product manufacturer includes the packaged semiconductor devices inthe circuitry of their product. Because of their packaging, the devicesare ready to be “plugged in” to the circuity assembly of the productthat the manufacturing is making. Because of their packaging, thedevices are protecting from the elements that might degrade or destroythe device. In addition, because of their packaging, the devices areinherently larger (e.g., typically 2-3 times) than the die found insidethe package. Thus, the resulting circuit assembly cannot be any thinnerthan the packaging of the semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a background view illustrating a conventional die-to-endproduct manufacture.

FIG. 2 is an example cross-sectional view of an electrophotographicdeposition for deposition of ferromagnetic semiconductor device dies ona substrate as described in present implementations herein.

FIG. 3 is a cross-sectional view of an example discrete packagedsemiconductor device (e.g., LED) as described in present implementationsherein.

FIG. 4 is an example implementation for transferring ferromagnetic diesfrom a developing unit component to a photosensitive drum component inan exemplary electrophotographic deposition technique as describedherein.

FIG. 5 is an example implementation of printing or performingsemiconductor device dies deposition onto the substrate.

FIG. 6 is a flow diagram illustrating an example process chart forimplementing, at least in part, the technology described herein.

The Detailed Description references the accompanying figures. In thefigures, the left-most digit(s) of a reference number identifies thefigure in which the reference number first appears. The same numbers areused throughout the drawings to reference like features and components.

DETAILED DESCRIPTION

Disclosed herein is a deposition of unpackaged semiconductor devicesonto a substrate. Herein, such devices may be called “semiconductordevice dies” or more simply “dies.” Example implementations describedherein include those where the unpackaged semiconductor devices includelight emitting devices (LED). In the described examples, the LED diesare disposed onto a substrate using techniques similar to thoseinvolving printing ink or toner onto paper like those ofelectrophotographic printing techniques.

As described herein, the fabricated dies are manufactured to beferromagnetic. A permanent iron magnet has ferromagnetic properties.However, not all ferromagnetic material includes iron. Indeed,ferromagnetism describes a property and behavior of material. Ingeneral, a ferromagnetic material is responsive to a magnetic field.

Herein, the dies described herein may be called “ferromagnetic” ormagnetic-field responsive (MFR). When exposed to an electro-magnetic(EM) field, the ferromagnetic die moves or orients itself to align withthe magnetic field. This aligns and orients the deposited dies so thatit electrical contacts are positioned in a functional manner. Anelectro-magnetic (EM) polarization may provide the orienting magneticfield. Such an EM polarization, for example, may be implemented intechniques akin to electrophotographic printing techniques.

For the electrophotographic printing techniques, a latent image of apre-configured outline of die placements (i.e., pre-configured circuitrylayout design) is first written in a photosensitive drum component of anelectrophotographic deposition. A developing unit component of theelectrophotographic deposition is then filled with ferromagnetic dies,which are to be aligned and subsequently transferred to thephotosensitive drum component. The alignment, for example, includes anapplication of the EM potential where the ferromagnetic dies aremobilized to form the pre-configured outline of die placements writtenas the latent image in the photosensitive drum component. In thisexample, the EM polarization is utilized to control horizontal and/orvertical (X and/or Y) orientations, direction, angular position, anddistribution of the dies based from the written latent image.

Thereafter, the aligned dies are transferred from the developing unitcomponent to the photosensitive drum component. Another alignment may beimplemented in the photosensitive drum component as may be necessary andafter which, a precision deposition of the aligned ferromagnetic dies isperformed onto the substrate.

The techniques described herein enable micro-precise deposition of thedies onto a substrate. Herein, micro-precise placement or depositioninvolves the die being placed within fifteen (15) microns (+/−15microns) of the intended target.

Typical Die-to-End-Product Meta-Manufacturing

FIG. 1 illustrates a conventional die-to-end-product meta-manufacture100. The meta-manufacture usually includes three parts:semiconductor-device-package manufacture 110, shipping/storage 150, andproduct manufacture 160.

The semiconductor-device-package manufacture 110 includes diefabrication 120, die sorting 130, and die packaging 140.

Before the die fabrication 120 starts, a wafer manufacturer supplies asemiconductor wafer. A typical wafer is sliced from ingots of silicon orother semiconductor material. Each wafer includes many (e.g., hundreds,thousands, or millions) of semiconductor devices. Semiconductor devicesare typically manufactured as single discrete devices or as integratedcircuits (ICs). Examples of single-discrete devices includelight-emitting diodes (LEDs), diodes, transistors, resistors, and thelike. For illustration purpose, the LED is a concrete example of asemiconductor device discussed herein. More particularly, the LED is theconcrete example of a single-discrete semiconductor device discussedherein.

The die fabrication 120 includes wafer mounting 121, wafer etching 122,die testing 123, wafer dicing 124, and wafer stretching 125. The diefabrication is sometimes called die preparation. Those of ordinary skillin the art view conventional die preparation as the step in thesemiconductor device fabrication in which a wafer is prepared forpackaging and/or testing.

During wafer mounting 121, the wafer is mounted on a stretchy low-tackadhesive tape that is itself attached to a ring. This tape may isgenerally called “dicing tape” or more commonly “blue tape,” since ittraditionally has a blue hue. Since the dicing tape holds or carries thewafer (and ultimately the dies) it is often generically called carriertape or more simply as the carrier.

The dicing tape is often made from flexible and stretch material (suchas polyvinyl chloride (PVC)) and has an adhesive (e.g., acrylic orsynthetic acrylic) bonded one side. The dicing type typically has a hightear strength, is flexible, and stretchy. Generally, one of the mainpurposes of the dicing tape is to ensure that the individual dies remainfirmly in place during dicing 124 of the wafer into separate dies.

After the wafer is mounted, the wafer is etched 122 and diced 124. Thewafer etching may also be called scoring. The wafer dicing may be calledsemiconductor-die cutting. Sometimes the combination of etching/dicingis called die singulation.

During the die singulation (e.g., etching 122 and dicing 124), the waferis cut into rectangular pieces, each called a die. In between thosefunctional parts of the circuits of the wafer, a thin non-functionalspacing is foreseen where a saw (or the like) can safely cut the waferwithout damaging the circuits of the semi-conductor devices in thewafer. Usually the dicing is performed with a water-cooled circular sawwith diamond-tipped teeth.

During the testing 123, each semiconductor device is subjected tovarious testing. From this testing, various properties of each device isdetermined and tracked. That is, a database or map of the devices of thewafer is created that records the determined properties of each device.Herein, this may be called “device map,” “die database,” or the like. Asdepicted in FIG. 1, the testing 123 is shown as occurring between theetching 122 and the dicing 124. In other instances, the testing canoccur at other points during the die fabrication 120.

Typically, the testing 123 involves testing the dies on the wafer withan electronics tester that pressing tiny probes against the die. Thetesting often involves determining the electrical functioning of thecircuitry of the die. For example, when a LED die is tested, itsluminance properties are tracked. Such luminance properties may includebrightness, color, and the like.

After the die singulation, the wafer is typically stretched 125. This isalso called wafer expansion. The dicing tape on which the wafer isadheared is stretched out radially to increase the spacing between thenow physically separated dies of the wafer. The typical reason for doingthis is to prevent die edge damage during shipping or during theconventional pick-and-place operation.

In many instances, the die sorting 130 occurs next after the diefabrication. This may be called die binning. The purpose of the diesorting is to collect like dies together in “bins.” The dies are sortedbased upon their properties as determined during the testing 123.

The die sorting 130 starts with the stretched wafer 125, which was theresult of the die fabrication 120. A pick-and-place machine 132 picks upindividual dies from the stretch wafer. As depicted, stretched wafer 133is a side elevation view of the same stretched wafer 125. Stretchedwafer 134 shows the same wafer 133 after one die has been removed. Thepick-and-place machine 132 places the dies into one or many “bins” 135(or binned carriers). The bins are often a matrix of dies on dicingtape. Each bin contains like or similar dies based upon one or moreproperties.

The pick-and-place machine 132 is the kind of machine commonly used byfabricators of semiconductor devices (e.g., LEDs) to transfer theirdevices from one location to another. In particular, such machines areused to pick a single-discrete device (e.g., LED) from one carrier tapeto another. As shown, with the die sorting 130, the pick-and-placemachine 132 picks a die off of the original carrier 133/134 and placesonto one of multiple binned carriers 135.

The packaging 140 stage starts with one of the binned carriers (shown ascarrier 141) of like dies. A pick-and-place machine 142 is shown pickinga die from a side elevation view of the carrier 143 and placing it intoa package mold 144. This is often called mounting. The packaging mold144 is often made of plastic or ceramic. At 145, wires are added toconnect the electrical contacts of the die to the packaging's externalcontacts. At 146, the mold is filled with an environmentally protectingsealant. Often, the die is capped as is shown at 147. If the die is anLED then often this cap is a lens to focus and direct the light.

Wikipedia.com describes a semiconductor package in this manner:

-   -   A semiconductor package may have as few as two leads or contacts        for devices such as diodes, or in the case of advanced        microprocessors, a package may have hundreds of connections.        Very small packages may be supported only by their wire leads.        ///    -   In addition to providing connections to the semiconductor and        handling waste heat, the semiconductor package must protect the        “chip” from the environment, particularly the ingress of        moisture. Stray particles or corrosion products inside the        package may degrade performance of the device or cause failure.        A hermetic package allows essentially no gas exchange with the        surroundings; such construction requires glass, ceramic or metal        enclosures.

As represented by packaged device 147, the packaged semiconductor device(e.g., an LED) is the sellable product that is the result of thesemiconductor-device-package manufacture 110.

The shipping/storage 150 part includes a warehouse 152 and shipping 154,156 to/from that warehouse. Typically, the packaged devices arepurchased by commercial enterprises, especially device/productmanufactures. Until such purchase, the packaged devices are stored. Theshipping/storage 150 part represents the typical scenario where themanufacturer of the packaged devices ships 152 their goods to awarehouse 154 for storage while awaiting orders or as part of adistribution system. From the warehouse 154, the purchased packageddevices are delivered 156 to a product manufacturer 170, for example.Sometimes the shipment/delivery (152/156) may be across a nation or anocean. That adds time and cost to the overall die-to-end-productmeta-manufacture 100.

The product manufacture 160 part includes the product manufacturer 170itself, construction 180 of the circuitry that will go into anelectronic product, and manufactured products 190.

The product manufacturer 170 is a company that creates and/or sells anelectronic device or product or some portion thereof. For example, theproduct manufacturer 170 may be an original equipment manufacturer(OEM). An OEM is a company that makes a part or subsystem that is usedin another company's end-product. Regardless, the final product that isbeing built has some electronic circuitry included therein.

At 180, that electronic circuitry is constructed. Such constructiontypically includes, for example, placing electronic components (e.g.,transistors, diodes, ICs, batteries, resistors, capacitors, and thelike) on a printed circuit board (PCB) and electronically linking suchcomponents using wires or other conduct tracks. Indeed, PCBs typicallyhave conductive layers and non-conductive layers. The PCB offersmechanical support and insulation for the electronic components andtheir conductive links.

The packaged devices (such as device 147) is an example of the type ofelectronic component that is used in the construction of electroniccircuitry at 180. Since the packaged device is already protected fromenvironmental elements, the constructed circuitry does not necessarilyneeds environmental protection.

One or more of the completed circuitry is assembled together with othermechanical and functional parts to form an intermediate sub-system orthe end-product itself. Regardless, at some point in the overall productmanufacturing process, the end-product is finally assembled and is readyto be distributed to customers and/or retail outlets. The end-productmay be most any device with electronic circuitry therein. Examples ofsuch end-products includes mobile phones, game controllers, digitalmusic players, digital cameras, toys, video game consoles, computerinput devices, medical devices, televisions, computers, appliances,automobiles, ebook readers, and the like.

Exemplary Tool

FIG. 2 illustrates an example cross-sectional view of anelectrophotographic die depositor 200 for precision deposition ofsemiconductor device dies onto a substrate. The semiconductor devicedies, for example, includes the unpackaged singulated dies as describedin FIG. 1 above. In this example, the electrophotographic die depositor200 is configured to facilitate formation or deposition of dies orunpackaged dies onto the substrate.

Typical electrophotographic printing is a printing technique used inlaser and light-emitting diode (LED) printers and most copy machines. Ituses electrostatic charges, dry ink (i.e., toner) and light. Aselenium-coated, photoconductive drum is positively charged. Using alaser or an array of LEDs, a negative of the to-be-printed image isbeamed onto the drum, cancelling the charge and leaving a positivelycharged replica of the original to-be-printed image. Then, thenegatively charged toner is attracted to the positive image on the drum,and the toner is then attracted to the paper, also positively charged.With typical electrophotographic printing, the final stage is fusing,which uses heat and pressure, pressure alone or light to cause the tonerto permanently adhere to the paper.

The electrophotographic die depositor 200 described herein depositsunpackaged semiconductor devices (i.e., dies) onto a substrate usingsome approaches akin to conventional electrophotographic deposition thatprints toner onto paper.

As shown here, the electrophotographic die depositor 200 may include alight-emission subsystem 202, a photosensitive drum 204, a developingunit 206 that is coupled to an EM potential supply 208, a charging unit210, a transfer charger 212, a substrate 214, a guiding roller 216, anda cleaning sheet 218. The electrophotographic die depositor 200 furtherincludes a printer controller 220 that may be coupled to an externaldevice 222 such as one or more computers, portable computing devices,substrate handling mechanics, or the like.

The light-emission subsystem 202 may be implemented by any suitablelight emission mechanism. For example, the light-emission subsystem 202may be a laser or an array of light-emitting diodes (LEDs). For thisexample, the light-emission subsystem may be called the laser 202.

As described herein, the external device 222 may be utilized as a sourceof a specified circuitry layout design or the pre-configured outline ofdie placements on the substrate 214. For example, the specifiedcircuitry layout design may be based upon previously formed layers ormaterials on the substrate 214, which may still be at earlymanufacturing stage prior to the deposition process as described herein.In this example, the specified circuitry layout design may include whatarea(s), portion(s), etc. on the layer of the substrate 214 may need tobe filled with the unpackaged semiconductor device dies (or simplydies).

In another example, the specified circuitry layout design may includemore or less the number of dies that is required to fill the particularareas or portions on the layer of the substrate 214. The required numberof semiconductor device dies, for example, may be based upon the shapeand configuration of each die, which may be known or pre-determinedprior to deposition process as described herein.

The printer controller 220 may receive the specified circuitry layoutdesign from the external device 222 in the form of input code data, andconverts the received input code data into an image data. The image datamay be used to modulate the lasers 202, which form an emission patternaccording to the image data and based upon a photosensitive surface ofthe photosensitive drum 204. After the light exposure of thephotosensitive surface of the photosensitive drum 204, a latent imageaccording to the emission pattern is formed on the photosensitive drum204. The latent image, for example, may include an image representationof the pre-configured outline of die placements or the specifiedcircuitry layout design of dies on the substrate 214.

The photosensitive drum 204 rotates in clockwise direction and isdisposed inside a main body of the electrophotographic deposition 200.Around the photosensitive drum 204 is the charging unit 210, whichfacilitates uniform charging of the surface of the photosensitive drum204, and the developing unit 206, which facilitates formation of a“toner” image by attaching dies to the photosensitive drum 204. Thetoner image, for example, corresponds to the latent image or theexposure pattern that was formed through emission of lights from thelaser 202.

As described herein, the die used with this implementation isferromagnetic. When exposed to an electro-magnetic (EM) field, theferromagnetic die moves or orients itself to align with the magneticfield. This aligns and orients the deposited dies so that it electricalcontacts are positioned in a functional manner. For example, thecontacts align with where existing or expected conductive links (e.g.,conductive traces or exposed conductive layers) will be or are.

An electro-magnetic (EM) polarization provides the orienting magneticfield. The ferromagnetism of the die facilitates position/orientationmobility of the ferromagnetic dies when exposed to the EM polarizationsgenerated by the EM potential 208.

With the ferromagnetic die, the developing unit 206 is filled with amany of the discrete ferromagnetic dies that have uniform shapes. Theseuniform shapes and specific number (if known) of ferromagnetic dies maybe used as computation variables in the specified circuitry layoutdesign. In other words, at each sequence of die deposition onto thesubstrate 214, the number and shapes of ferromagnetic dies in thedeveloping unit 206 are pre-configured to more or less complete therequired number of ferromagnetic dies to be formed onto the substrate214.

The developing unit 206 may be configured to align the ferromagneticdies based from the pre-configured outline of die placements, which issimilar to the formed latent image in the photosensitive drum 204. Asdescribed herein, the developing unit 206 receives different EMpolarizations that are generated by the EM potential 208. The controlledapplication of EM polarizations, for example, are utilized to align andmanipulate the orientation, angular position, symmetry, and the like, ofeach ferromagnetic die with respect to another ferromagnetic die. Inthis example, the controlled application of EM polarizations maycorrespond to certain attraction or repulsion of the dopant materialformed on the ferromagnetic dies. Furthermore, after the controlledapplication of the EM polarization, the developing unit 206 may beconfigured to detect substantial alignment of the ferromagnetic dieswith the use of a sensor (not shown). The substantial alignment in thiscase is based from the specified circuitry layout design that wassupplied by the external device 222.

After the alignment of the ferromagnetic dies in the developing unit206, the aligned ferromagnetic dies are transferred and attached to thelatent image formed on the photosensitive drum 204. The transfer of thealigned ferromagnetic dies may follow the exposure pattern based fromthe pre-configured outline of the ferromagnetic die placements in thesubstrate 214. Furthermore, the transfer of the aligned ferromagneticdies may be implemented individually and at a certain frequency untilthe desired latent image is filled with ferromagnetic dies.

At the bottom of the photosensitive drum 204 is the transfer charger 212that is configured to facilitate transfer of the attached ferromagneticdies from the photosensitive drum 204 onto the substrate 214. Forexample, the substrate 214 passes between the photosensitive drum 204and the transfer charger 212 during the actual deposition of theferromagnetic dies from the photosensitive drum 204 onto the substrate214. In this example, the transfer charger 212 is configured to providethe electrostatic charges in detaching the formed ferromagnetic die fromthe photosensitive drum 204 onto the substrate 214.

With continuing reference to FIG. 2, the cleaning means 218 may collectthe ferromagnetic dies left behind on the photosensitive drum 204 afterthe deposition process for the present sequence. The movement of thesubstrate 214 is controlled by the guide roller 216 and another sequenceof precision deposition of dies may be carried out as necessary untilthe specified circuitry layout design from the external device 222 iscompleted.

Exemplary Implementation

FIG. 3 is a cross-sectional view of an example discrete packaged LED 300that is the formed, at least in part, from the techniques describedherein.

As shown, the packaged LED 300 includes a top conductive layer 302 and abottom conductive layer 304. Alternatively, these may be formed byconductive traces on either side of the die. As showed, sandwiched inbetween these conductive layers 302 and 304 is a middle layer thatcontains light-generating sources 306 (such as LEDs). In particular, thelight-generating sources 306 includes the formed ferromagnetic dies thatwere printed by the electrophotographic die depositor 200 as describedin FIG. 2 above.

The packaged LED 300 further shows a dielectric layer 308 surroundingthe light-generating sources 306, and a translucent or transparent thinfilm 300 (e.g., polyester) or other coating that is positioned at thetop most layer of the packaged LED 300. The dielectric layer 308, forexample, is made of ceramic or plastic material to isolate the topconductive layer 302 from the bottom conductive layer 304. On the otherhand, the transparent thin film 310 may direct light beams or reflectionof the dies from the light-generating sources 306.

Going back to FIG. 2, the deposition of the ferromagnetic dies may bebased upon the formed layers or materials on the substrate 214, whichmay still be at the early manufacturing stage prior to the depositionprocess as described herein. In relation to the packaged LED 300 in FIG.3, the deposition process (i.e., of ferromagnetic dies) may be performedafter the formation of at least the conductive layer 304 on top of thesubstrate 214.

For example, the conductive layer 304 is first patterned and formed onthe substrate 214. In this example, the deposition process may beperformed subsequently to form the light-generating sources 306. Thedeposition process, for example, is implemented through theelectrophotographic printing technique as described in FIG. 2 above.

After the formation of the light-generating sources 306 onto theconductive layer 304, the dielectric layer 308, the conductive layer302, and the translucent thin film 310 may be formed subsequently on thesubstrate 214. In other implementations, the deposition process may beimplemented after the formation of the bottom conductive layer 304 andthe dielectric layer 308 onto the substrate 214. In this otherimplementation, the pre-configured outline of die placements may includethe number and shapes of ferromagnetic dies that are required to fillthe desired circuitry layout in between the dielectric layer 308.

FIG. 4 is an example implementation for transferring ferromagnetic diesfrom the developing unit component to the photosensitive drum componentin the exemplary electrophotographic deposition technique.

As shown here, uniformly shaped ferromagnetic dies 400 are disposedpartially or wholly on outer perimeter of the die. For example, thedopant material is formed as a line across the width or length of theunpackaged die, formed as dots at each end of the unpackaged die, formedin an uneven manner across the unpackaged die, or the like. In thisexample, the controlled application the EM polarization, which exerts acorresponding pico-newton force onto the dopant material, may facilitatealignment of the ferromagnetic dies 400 based on the formation of thedopant material in the unpackaged die.

With the aligned ferromagnetic dies 400, each ferromagnetic die 400 istransferred individually to the photosensitive drum 204. The transfer,for example, may be implemented by controlling the electrostatic chargein the photosensitive drum 204 to attract the aligned ferromagnetic die400 from the developing unit 206. Furthermore, the transfer of theferromagnetic dies 400, which were aligned to correspond with the formedlatent image in the photosensitive drum 204, may be implementedsequentially.

For example, the formed latent image at the photosensitive drum 204 mayrequire different ferromagnetic die configurations such as coloredferromagnetic dies, low-beam ferromagnetic dies, or the like, for aparticular area on the substrate 214. In this example, the deposition ofdifferently configured ferromagnetic dies 400 may be implementedsequentially by separating the deposition process for eachconfiguration. The first sequence, for example, includes a deposition ofwhite colored ferromagnetic dies 400 onto a first area on the substrate214. The second sequence, for example, includes deposition of shadedferromagnetic dies 400 on another area of the substrate 214, and so onuntil the specified circuitry layout design in completed.

Although FIG. 4 illustrates a pre-alignment of all ferromagnetic die 400for each sequence, individual alignment of each ferromagnetic die 400may be implemented prior to transferring of the individual ferromagneticdie 400 to the photosensitive drum 204.

FIG. 5 illustrates an example implementation of printing or performingferromagnetic die (e.g., die) deposition onto the substrate.

As shown here, the attached ferromagnetic dies 400 on the photosensitivedrum 204 are transferred, printed, or deposited onto the substrate 214.In this scenario, the transfer charger 212 is configured to provide theelectrostatic charges in detaching the formed ferromagnetic dies 400from the photosensitive drum 204 onto the substrate 214 for eachsequence of the deposition process. In other words, the substrate 214may move backward or forward for each sequence of the deposition processuntil the desired specified circuitry layout design is completed.

Exemplary Process

FIG. 6 is a flow diagram illustrating an example process chart 600 forimplementing, at least in part, the technology described herein. Inparticular, process 600 depicts a precision deposition of ferromagneticdies using an electrophotographic printing technique.

At block 602, a latent image of a pre-configured outline of dieplacements is written to form a latent image in a photosensitive drumcomponent. For example, the pre-configured outline of die placementsincludes a specified circuitry layout design of ferromagnetic dies thatwill be printed on a particular area or portions of the substrate. Inthis example, the substrate may include a formed layer such as theconductive layer 304 (FIG. 3) for a first terminal connection of theferromagnetic dies.

At block 604, ferromagnetic dies are placed onto a developing unitcomponent of the electrophotographic deposition. In the above example,specific number and shapes of ferromagnetic dies are positioned onto thedeveloping unit based upon the deposition process sequence to beperformed. For each sequence, the developing unit is configuredfacilitate alignment of the ferromagnetic dies through a controlledapplication of EM potential or polarizations.

At the developing unit component, the controlled application of the EMpotential may align the orientation, direction, angular position, etc.of the ferromagnetic dies for the present deposition sequence to beperformed. The alignment, for example, is based from the pre-configuredoutline of the semiconductor device dies placement.

At bock 606, the photosensitive drum component is configured to includeelectrostatic charges based on the specified circuitry layout of thesemiconductor device dies. For example, the charging unit 210 mayprovide formation of electrostatic charges on the photosensitive drum204. In this example, the electrostatic charges may further facilitatere-alignment of the ferromagnetic dies to overcome the effect offriction and air gap between the photosensitive drum 204 and thedeveloping unit 206.

At block 608, the aligned ferromagnetic dies at the developing unitcomponent are transferred to the photosensitive drum component. Forexample, the electrostatic charges at the photosensitive drum 204 areconfigured to attract the aligned ferromagnetic dies from the developingunit 206. In this example, the electrostatic charges may furtherminimize the effect of friction and air gap in between thephotosensitive drum 204 and the developing unit 206.

At block 610, deposition of the aligned ferromagnetic dies is performedonto the substrate. For example, with the use of the electrophotographicdeposition technique, deposition of the dies may be performed on thesubstrate by transferring or printing of the aligned ferromagnetic diesfrom the photosensitive drum component onto the substrate.

Additional and Alternative Implementation Notes

The dies described herein may be LEDs. More particularly, they may bemicroLEDs. MicroLEDs are 5-100 microns in diameter. Some implementationsdescribed herein use LEDs with a diameter of 15-50 microns. Still otherimplementations use LEDs having a diameter of 20-30 microns.

As used herein, semiconductor device refers to both single discretedevices or as integrated circuits (ICs). As used herein, a reference toa single-discrete semiconductor device (“SD semiconductor device)expressly excludes ICs, but includes devices such as light-emittingdiodes (LEDs), diodes, transistors, resistors, and the like. Unless thecontext indicates otherwise, the term “semiconductor device die” orsimply “die” refers to an unpackaged semiconductor device.

The ferromagnetic dies described herein may be manufactured frommagnetic semiconductors. Magnetic semiconductors are semiconductormaterials that exhibit both responsiveness to a magnetic fields (e.g.,ferromagnetism) and useful semiconductor properties. Example magneticsemiconductors are made from one or more of the following:Manganese-doped indium arsenide and gallium arsenide (GaMnAs),Manganese-doped indium antimonide, manganese- and iron-doped indiumoxide, manganese-doped zinc oxide, n-type cobalt-doped zinc oxide,cobalt-doped titanium dioxide (both rutile and anatase), chromium-dopedrutile, iron-doped rutile and iron-doped anatase, nickel-doped anatase,manganese-doped tin dioxide, iron-doped tin dioxide, strontium-doped tindioxide (SrSnO₂), europium oxide, and chromium doped aluminium nitride.

Like the paper used in a traditional electrophotographic deposition, thesubstrate described herein is made from material that is both thin andflexible. Examples of such material includes polyethylene terephthalate(PET), polyester, polyvinyl chloride (PVC), a polymide film (such asKapton™), or the like.

In the above description of exemplary implementations, for purposes ofexplanation, specific numbers, materials configurations, and otherdetails are set forth in order to better explain the present invention,as claimed. However, it will be apparent to one skilled in the art thatthe claimed invention may be practiced using different details than theexemplary ones described herein. In other instances, well-known featuresare omitted or simplified to clarify the description of the exemplaryimplementations.

The inventors intend the described exemplary implementations to beprimarily examples. The inventors do not intend these exemplaryimplementations to limit the scope of the appended claims. Rather, theinventors have contemplated that the claimed invention might also beembodied and implemented in other ways, in conjunction with otherpresent or future technologies.

Moreover, the word “exemplary” is used herein to mean serving as anexample, instance, or illustration. Any aspect or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs. Rather, use of the wordexemplary is intended to present concepts and techniques in a concretefashion. The term “techniques,” for instance, may refer to one or moredevices, apparatuses, systems, methods, articles of manufacture, and/orcomputer-readable instructions as indicated by the context describedherein.

As used in this application, the term “or” is intended to mean aninclusive “or” rather than an exclusive “or.” That is, unless specifiedotherwise or clear from context, “X employs A or B” is intended to meanany of the natural inclusive permutations. That is, if X employs A; Xemploys B; or X employs both A and B, then “X employs A or B” issatisfied under any of the foregoing instances. In addition, thearticles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more,” unlessspecified otherwise or clear from context to be directed to a singularform.

These processes are illustrated as a collection of blocks in a logicalflow graph, which represents a sequence of operations that can beimplemented in mechanics alone or a combination with hardware, software,and/or firmware. In the context of software/firmware, the blocksrepresent instructions stored on one or more computer-readable storagemedia that, when executed by one or more processors, perform the recitedoperations.

Note that the order in which the processes are described is not intendedto be construed as a limitation, and any number of the described processblocks can be combined in any order to implement the processes or analternate process. Additionally, individual blocks may be deleted fromthe processes without departing from the spirit and scope of the subjectmatter described herein.

Other Ways of Describing Implementations

Below is a listing of different ways to describe the implementationsintroduced here:

Example A

A method of electrophotographic deposition of unpackaged semiconductordevices (“dies”), the method comprising writing a latent image on aphotosensitive drum, wherein the latent image includes a pre-configuredoutline of die placements that will be deposited onto a substrate,providing a developing unit filled with ferromagnetic dies, aligning theferromagnetic dies in the developing unit to conform with the latentimage on the photosensitive drum, wherein the aligning includes acontrolled application of an electro-magnetic (EM) polarization toaffect a physical orientation of each ferromagnetic die configuring thephotosensitive drum to include an electro-static charge, transferringthe aligned ferromagnetic dies from the developing unit to thephotosensitive drum, and depositing the ferromagnetic dies onto thesubstrate.

The subject matter of Example A can optionally include a ferromagneticdie that is a light-emitting diode (LED) die.

The subject matter of Example A can optionally include thepre-configured outline of die placements includes a defined number ofuniformly shaped ferromagnetic dies that will be printed in a particularlocation or area of the substrate.

The subject matter of Example A can optionally include ferromagneticdies which include magnetic semiconductor material.

The subject matter of Example A where the magnetic semiconductormaterial is formed partially or wholly on an outer perimeter of the die.

The subject matter of Example A, where the controlled application of theEM polarization exerts a corresponding pico-newton force onto themagnetic semiconductor material, wherein the exerted pico-newton forcefacilitates alignment of at least one of the ferromagnetic dies.

The subject matter of Example A, where the writing of the latent imageon the photosensitive drum is facilitated by a light-emission subsystem,wherein an emission in light is modulated by an image representation ofthe pre-configured outline of unpackaged die placements.

The subject matter of Example A, where the physical orientation includeshorizontal (X), vertical (Y), and angular positions.

The subject matter of Example A, where the transferring of the alignedferromagnetic dies includes an individual transfer of alignedferromagnetic die.

The subject matter of Example A can optionally include realigning of thetransferred ferromagnetic dies in the photosensitive drum, wherein therealigning is based from an effect of friction and an air-gap in betweenthe photosensitive drum and the developing unit.

Example B

A device comprising a light-emission subsystem configured to emit alight-emission pattern based upon a pre-configured outline of unpackagedsemiconductor device (“die”) placements that will be printed on asubstrate, a photosensitive drum configured to receive thelight-emission pattern that facilitates formation of a latent image on aphotosensitive surface of the photosensitive drum, the latent image isan image representation of the pre-configured outline of die placements,a developing unit configured to receive and align ferromagnetic dies,wherein the aligned ferromagnetic dies are transferred by the developingunit to the photosensitive drum, and a transfer charger configured tofacilitate deposition of the aligned ferromagnetic dies from thephotosensitive drum to the substrate.

The device described in Example B can optionally include a light fromthe light-emission subsystem that is modulated by image data that isbased from input code data from an external device.

The device described in Example B can optionally include a ferromagneticdie that is a light-emitting diode (LED) die.

The device as described in Example B can optionally in cudea developingunit that aligns the ferromagnetic dies through a controlled applicationof an electromagnetic (EM) polarization that changes a physicalorientation of each ferromagnetic die.

The device described in Example B can optionally include an EM potentialsupply configured to supply the EM polarization.

Example C

An apparatus comprising an external device configured to supply inputcode data, wherein the input code data is a specified circuitry layoutdesign of unpackaged semiconductor device (“die”) placements that willbe printed on a substrate, a printer controller configured to receiveand convert the input code data into image data, a light emissionsubsystem configured to emit a light-emission pattern based upon theimage data, a photosensitive drum configured to receive thelight-emission pattern that facilitates formation of a latent image on aphotosensitive surface of the photosensitive drum, the latent image isan image representation of the image data, a developing unit configuredto receive and align ferromagnetic dies, wherein the alignedferromagnetic dies are transferred by the developing unit to thephotosensitive drum, and a transfer charger configured to facilitatedeposition of the aligned ferromagnetic dies from the photosensitivedrum to the substrate.

The apparatus described in Example C can optionally include aferromagnetic die which is a light-emitting diode (LED) die.

The apparatus described in Example C can optionally include a developingunit which aligns the ferromagnetic dies through a controlledapplication of an electromagnetic (EM) polarization that changes aphysical orientation of each ferromagnetic die.

The apparatus described in Example C can optionally include an EMpotential supply configured to supply the EM polarization.

The apparatus described in Example C can optionally include a chargingunit configured to supply uniform electrostatic charges to thephotosensitive drum to hold the transferred aligned ferromagnetic diesfrom the developing unit.

What is claimed is:
 1. A method of electrophotographic deposition ofunpackaged semiconductor devices (“dies”), the method comprising:writing a latent image on a photosensitive drum, wherein the latentimage includes a pre-configured outline of die placements that will bedeposited onto a substrate; providing a developing unit filled withferromagnetic dies; aligning the ferromagnetic dies in the developingunit to conform with the latent image on the photosensitive drum,wherein the aligning includes a controlled application of anelectro-magnetic (EM) polarization to affect a physical orientation ofeach ferromagnetic die; configuring the photosensitive drum to includean electro-static charge; transferring the aligned ferromagnetic diesfrom the developing unit to the photosensitive drum; depositing theferromagnetic dies onto the substrate.
 2. The method as recited in claim1, wherein the ferromagnetic die is a light-emitting diode (LED) die. 3.The method as recited in claim 1, wherein the pre-configured outline ofdie placements includes a defined number of uniformly shapedferromagnetic dies that will be printed in a particular location or areaof the substrate.
 4. The method as recited in claim 1, wherein theferromagnetic dies include magnetic semiconductor material.
 5. Themethod as recited in claim 4, wherein the magnetic semiconductormaterial is formed partially or wholly on an outer perimeter of the die.6. The method as recited in claim 5, wherein the controlled applicationof the EM polarization exerts a corresponding pico-newton force onto themagnetic semiconductor material, wherein the exerted pico-newton forcefacilitates alignment of at least one of the ferromagnetic dies.
 7. Themethod as recited in claim 1, wherein the writing of the latent image onthe photosensitive drum is facilitated by a light-emission subsystem,wherein an emission in light is modulated by an image representation ofthe pre-configured outline of unpackaged die placements.
 8. The methodas recited in claim 1, wherein the physical orientation includeshorizontal (X), vertical (Y), and angular positions.
 9. The method asrecited in claim 1, wherein the transferring of the alignedferromagnetic dies includes an individual transfer of alignedferromagnetic die.
 10. The method as recited in claim 1 furthercomprising: realigning of the transferred ferromagnetic dies in thephotosensitive drum, wherein the realigning is based from an effect offriction and an air-gap in between the photosensitive drum and thedeveloping unit.
 11. A device comprising: a light-emission subsystemconfigured to emit a light-emission pattern based upon a pre-configuredoutline of unpackaged semiconductor device (“die”) placements that willbe printed on a substrate; a photosensitive drum configured to receivethe light-emission pattern that facilitates formation of a latent imageon a photosensitive surface of the photosensitive drum, the latent imageis an image representation of the pre-configured outline of dieplacements; a developing unit configured to receive and alignferromagnetic dies, wherein the aligned ferromagnetic dies aretransferred by the developing unit to the photosensitive drum; atransfer charger configured to facilitate deposition of the alignedferromagnetic dies from the photosensitive drum to the substrate. 12.The device as recited in claim 11, wherein the light from thelight-emission subsystem is modulated by image data that is based frominput code data from an external device.
 13. The device as recited inclaim 11, wherein the ferromagnetic die is a light-emitting diode (LED)die.
 14. The device as recited in claim 11, wherein developing unitaligns the ferromagnetic dies through a controlled application of anelectromagnetic (EM) polarization that changes a physical orientation ofeach ferromagnetic die.
 15. The device as recited in claim 14 furthercomprising an EM potential supply configured to supply the EMpolarization.
 16. An apparatus comprising: an external device configuredto supply input code data, wherein the input code data is a specifiedcircuitry layout design of unpackaged semiconductor device (“die”)placements that will be printed on a substrate; a printer controllerconfigured to receive and convert the input code data into image data; alight emission subsystem configured to emit a light-emission patternbased upon the image data; a photosensitive drum configured to receivethe light-emission pattern that facilitates formation of a latent imageon a photosensitive surface of the photosensitive drum, the latent imageis an image representation of the image data; a developing unitconfigured to receive and align ferromagnetic dies, wherein the alignedferromagnetic dies are transferred by the developing unit to thephotosensitive drum; a transfer charger configured to facilitatedeposition of the aligned ferromagnetic dies from the photosensitivedrum to the substrate.
 17. The apparatus as recited in claim 16, whereinthe ferromagnetic die is a light-emitting diode (LED) die.
 18. Theapparatus as recited in claim 16, wherein developing unit aligns theferromagnetic dies through a controlled application of anelectromagnetic (EM) polarization that changes a physical orientation ofeach ferromagnetic die.
 19. The apparatus as recited in claim 18 furthercomprising an EM potential supply configured to supply the EMpolarization.
 20. The apparatus as recited in claim 18 furthercomprising a charging unit configured to supply uniform electrostaticcharges to the photosensitive drum to hold the transferred alignedferromagnetic dies from the developing unit.